SENSE OF TOUCH: PARTS, HOW IT WORKS AND FUNCTIONS - BIOLOGY - 2025

The sense of touch is one of the five basic systems that allow us to relate to our environment and perceive certain qualities of our environment. Through it, we can feel characteristics such as temperature, hardness, pressure, smoothness or roughness. Some experts also include pain perception within this system.

The most important sense organ for the sense of touch is the skin. In it, we can find different types of nerve receptors, which translate the information received from the outside into impulses that can be understood and interpreted by the brain. On the other hand, it is possible to find some of these receptors in other body organs.

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The sense of touch is vital to our survival. Some scientists believe that without their functions, it would be impossible for humans to survive, contrary to what happens with sight, hearing, taste or smell. However, researching on it is quite complicated, so we do not have as much data as we would expect.

The main difficulty in investigating touch is that its main sensory organ (the skin) extends throughout the body, instead of there being a single place where receptors are isolated as is the case with the rest of the senses. Even so, in this article we tell you everything we know about touch so far.

Parts (organs)

We have already mentioned that the main element related to touch is the skin. Although we don't normally think of it as a single organ, it is the largest in the entire body and one of the most important. All types of touch receptors that exist are concentrated in the skin.

On the other hand, today we also know that there are touch receptors in other areas of the body. These are not as abundant as those of the skin, but they fulfill the fundamental function of informing us about the state of our internal organs.

Skin

Human skin. Gabrielzerrisuela

The skin is the organ that covers our entire body externally. Its functions include protection against external agents such as microbes, maintaining the temperature of our body, and the perception of tactile stimuli and their transformation into impulses that can be interpreted by the brain.

The skin is made up of three layers: epidermis, dermis, and subcutis. The epidermis is the outermost, and is approximately two-tenths of a millimeter thick. It is composed of a large number of layers of flat epithelial tissue; and in it melanin is produced, which is the substance that gives our skin its color.

Second we have the dermis. It is a more elastic layer than the first, due to the collagen fibers it incorporates; and in it we can find a large number of blood vessels and components of the lymphatic system. In this layer we can find all the skin glands (odorous, sweaty and sebaceous).

At the same time, in the dermis there are nerve endings and receptors that allow us to perceive tactile sensations. Later we will see what are the different types that exist and the functions that each one of them fulfills.

Finally, the subcutis is a layer composed of connective tissue. Its main function is to maintain the temperature of our body and serve as an energy store, which is why adipose tissue also accumulates in this area. Depending on the area of ​​the body, the accumulation of fat will be greater or less.

Types of receptors in the skin

As we have already seen, in the layer of the skin known as the dermis we can find different receptors that allow us to receive tactile information and convert it into electrical signals that can be interpreted by our brain. Next we will study the most important types that exist.

Free nerve endings

The simplest touch receptors without simple nerve endings that end in the dermis and that help us perceive sensations such as touch, temperature, itching and pain. These are neurons whose dendrites end in the middle layer of the skin, as well as in the connective tissue under the dermis.

Free nerve endings are the most abundant touch receptors in the entire body, and those that help us to perceive most of the sensations related to this sense.

Pacini corpuscles

These receptors are also found in the dermis and in the connective tissue under the skin. However, at the same time we can find them in some internal structures, such as viscera or bones. These are large, oval-shaped receivers.

The corpuscles of Pacini are made up of a single nerve cell, which is covered by a capsule. Its main function is to allow us to perceive stimuli related to touch and pressure.

Meissner corpuscles

Meissner corpuscles are very sensitive receptors to the different sensations related to touch. They are found in very high concentrations in the most perceptual areas of our body, such as the tip of the tongue or the fingertips.

These receptors are formed by a capsule inside which are several cells superimposed on each other.

Ruffini corpuscles

Ruffini's corpuscles are located both in the dermis and in the connective tissue that we have under the skin. They are made up of neurons with many branches, covered by a capsule. Today, it is not known exactly what its function is.

In the past, it was believed that Ruffini's corpuscles were simply used to detect temperature. However, recent discoveries suggest that these receptors could also play a role in the detection of tactile stimuli.

Krause corpuscles

These skin receptors, located in the dermis, have the main function of allowing us to detect cold. They have a shape similar to those of Ruffini, being formed by a nerve ending with many branches, which in turn is covered by a mace-shaped capsule.

Golgi corpuscles

The latter type of sensory receptor serves to detect information about the state of contraction and tension of the muscles. They are, therefore, in the tissue that surrounds both the muscle fibers and the tendons.

Like Pacini corpuscles, Golgi corpuscles are made up of a single cell covered by a capsule.

Receptors in other parts of the body

Some of the receptors for the sense of touch are not only located on the skin, but can be found in other areas of the body. Thus, organs such as muscles or viscera have certain nerve endings designed to provide us with information about the internal state of our body.

Nociceptors

Some researchers consider that pain detection is also part of the functions of the sense of touch. Due to this, the receptors that we have already seen should be added one last type: nociceptors.

These touch receptors are located throughout the dermis, as well as in some internal organs. Its main function is to perceive harmful stimuli, and translate them into nerve impulses that are transmitted to the brain. Once there, he interprets them as pain.

How does the sense of touch work?

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The functioning of the sense of touch is very similar to that of the other four main senses. Tactile receptors (mechanoreceptors, thermoreceptors, and nociceptors) detect stimuli related to factors such as pressure, roughness, temperature, or pain. These stimuli can come both from outside the body and from within the body.

Once a receptor has detected a stimulus for which it is sensitive, it sends a signal to the brain via afferent neurons. These connect the sensory organs with the central nervous system through the spinal cord.

The signals picked up by the sense organs are then interpreted by the corresponding areas of the brain. The processing of tactile stimuli occupies a large percentage of the brain surface, because the information collected by this sense is essential for survival.

Finally, the brain sends a response through the efferent neurons to the corresponding effector organs, depending on the type of stimulus that has been received and what it implies for the body.

Features

The sense of touch fulfills a series of fundamental functions for our survival. On the one hand, it allows us to know where the limits of our body are, by perceiving sensations such as pressure, heat or pain when coming into contact with objects external to our body.

On the other hand, the sense of touch also allows us to know if there is some kind of problem within our body, especially in our internal organs, muscles or bones. This is why we have certain pain receptors in our guts and in other internal tissues.

Touch also helps us to perceive external dangers, such as objects that may harm us in some way. Thanks to this sense, we can react to threats and avoid suffering very negative consequences.

Lastly, touch allows us to collect valuable information about our environment and about the objects and living things with which we interact.

References

1. "Organs of the senses: touch" in: ABC Color. Retrieved on: March 15, 2019 from ABC Color: abc.com.py.
2. "Organ of the sense of touch" in: Academia. Retrieved on: March 15, 2019 from Academia: academia.edu.
3. "Touch" in: Wikipedia. Retrieved on: March 15, 2019 from Wikipedia: es.wikipedia.org.
4. "Touch: organs of the senses" in: History and Biographies. Retrieved on: March 15, 2019 from History and Biographies: historiaybiografias.com.
5. "Somatosensory system" in: Wikipedia. Retrieved on: March 15, 2019 from Wikipedia: en.wikipedia.org.